AMEL and Tram S.A. until June 2011 were subsidiaries of Attiko Metro S.A. (Greek: Αττικό Μετρό Α.Ε.

[4][5] Hellenic Train (formerly Trainose until May 2022) S.A., which absorbed the former Proastiakos S.A. in 2007, became independent of the OSE group in 2008 and until 2017 it is a separate private company.

OASA regularly conducts street photography and videography competitions both in black-and-white and in colour for photos taken while inside its means of transport.

Their replacement was a money box placed at the front end of the vehicles, next to the driver, where passengers would deposit their fare in cash, usually coinage.

In addition to ATH.ENA Ticket and ATH.ENA Card, OASA introduced the contactless payment system in Athens and surrounding areas, which is codenamed tap2ride.

[9]It was introduced on a pilot basis in Athens International Airport Express buses (Χ93, Χ95, Χ96, Χ97) on 24 April 2024.